Nuclear import of CaMV P6 is required for infection and suppression of the RNA silencing factor DRB4
Nuclear import of CaMV P6 is required for infection and suppression of the RNA silencing factor DRB4
复制标题
DOI：
10.1038/emboj.2008.129
复制
发表时间：
2008-08-06
期刊：
影响因子：
11.4
通讯作者：
Voinnet, Olivier
中科院分区：
文献类型：
--
作者：
Haas, Gabrielle;Azevedo, Jacinthe;Voinnet, Olivier
花椰菜花叶病毒（CaMV）是一种植物双链DNA病毒，其复制需要病毒翻译反式激活蛋白P6。虽然已知P6形成细胞质包涵体（病毒颗粒），但迄今为止被认为是病毒生物学所必需的，但一部分蛋白质也存在于细胞核中。在这里，我们报告说，单体P6进口到细胞核通过两个进口α-依赖的核定位信号，并表明这一过程是强制性的CaMV感染性，是独立的翻译转录和病毒质的形成。P6的一个核功能是抑制RNA沉默，这是一种具有抗病毒作用的基因调控机制，通常由专用的病毒抑制蛋白（病毒沉默抑制子; VSR）抵消。转基因P6在拟南芥中的表达在遗传上等同于使核蛋白DRB 4失活，该核蛋白DRB 4促进主要植物抗病毒沉默因子DCL 4的活性。我们进一步表明，一部分P6免疫沉淀与DRB 4在CaMV感染的细胞。这项研究确定了VSR与宿主RNA沉默组分之间的遗传和物理相互作用，并强调了亚细胞区室化在VSR功能中的重要性。
Replication of Cauliflower mosaic virus (CaMV), a plant double-stranded DNA virus, requires the viral translational transactivator protein P6. Although P6 is known to form cytoplasmic inclusion bodies (viroplasms) so far considered essential for virus biology, a fraction of the protein is also present in the nucleus. Here, we report that monomeric P6 is imported into the nucleus through two importin-alpha-dependent nuclear localization signals, and show that this process is mandatory for CaMV infectivity and is independent of translational transactivation and viroplasm formation. One nuclear function of P6 is to suppress RNA silencing, a gene regulation mechanism with antiviral roles, commonly counteracted by dedicated viral suppressor proteins (viral silencing suppressors; VSRs). Transgenic P6 expression in Arabidopsis is genetically equivalent to inactivating the nuclear protein DRB4 that facilitates the activity of the major plant antiviral silencing factor DCL4. We further show that a fraction of P6 immunoprecipitates with DRB4 in CaMV-infected cells. This study identifies both genetic and physical interactions between a VSR to a host RNA silencing component, and highlights the importance of subcellular compartmentalization in VSR function.